It is a well-known concern of individuals involved in semiconductor research and development that analytically evaluating semiconductor wafers within the confines of a clean room facility is an expensive and time consuming proposition. Test equipment occupies costly clean room floor space and special dress requirements for process monitoring personnel is both time consuming and inconvenient.
In greater detail, semiconductor wafers are manufactured in clean room environments during which noncontact and non-destructive analytical evaluations are performed to monitor process steps as required. Typically these analytical tests are performed in the confines of clean rooms having a class environment rating appropriate for the type of semiconductor devices being manufactured. The analysis can be by electromagnetic radiation such as X-rays or visible light. One typical example would be to determine the characteristics of a wafer surface after the completion of a particular process step. To prevent the contamination of a wafer, it must at all times during the manufacturing and process monitoring cycles be kept in a clean room environment.
Clean room facilities of the type required for modern semiconductor wafer manufacturing have been built utilizing the height of three stories of a building. Of these three stories, the clean room is typically the middle story and is sandwiched between two floors which house expensive air purification equipment. A portion of this expensive floor space is simply required for storing equipment which is needed for monitoring process steps and which obviously dictates the minimum floor space needed for the manufacturing of semiconductor wafers.
When working within a clean room environment all personnel are required to wear special clothing to help maintain the clean room environment. This clothing must be donned before entering the clean environment and removed after they leave. This is an inconvenient and time consuming process. In particular the process monitoring personnel who are required only for monitoring process steps must enter and exit the clean room environment many times daily.
Analysis methods may require special equipment which cannot be modified or adapted for use within clean room environments and therefore semiconductor wafers which are removed from the clean room environment for evaluation are typically thrown in the garbage once the evaluation is finished for fear of contamination. Equipment that is compatible with clean room environments is very expensive and even then must first be precleaned before being placed within the clean room environment. As well all equipment for use within the clean room environment must only use internal lubricants which are compatible for use within a clean room facility.